Mike, In this lifetime I believe that anything is possible, and if it's possible, then it will break at some point. But, without pictures, flow rates, static pressure readings and pressure readings on the pipe when the irrigation system is on and off, your questions being answered could be beyonf the scope of this forum.
What you are telling us *shouldn't* happen, but i'm sure that it could be possible depending on the pipe, location of fittings, pressure and flow rates.
You might want to bring in a pro to duplicate it and get pressure and flow readings when the system is on. Get the pro to run the system during the day and test the flow and pressure rates and check the plumbing.